Vaccum-generating unit

ABSTRACT

A main body comprises first to third block members composed of resin materials. A nozzle hole and a diffuser hole are integrally formed in the third block member. A suction passage is provided between the nozzle hole and the diffuser hole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vacuum-generating unit capable ofapplying a negative pressure to a suction mechanism such as a suctionpad.

2. Description of the Related Art

A vacuum supply apparatus has been hitherto utilized as a means forapplying a negative pressure to a suction pad. Such a vacuum supplyapparatus generally comprises: an ejector for generating a negativepressure; a vacuum port connected to and communicated with a suctionmechanism such as a suction pad via a tube; a valve mechanism providedwith a pressure fluid-supplying solenoid valve and a vacuum-breakingsolenoid valve for feeding compressed air to the ejector and the vacuumport and cutting off the supply of the compressed air; and a vacuumswitch for detecting the negative pressure generated in the vacuum port(see, for example, Japanese Laid-Open Utility Model Publication No.61-9599).

In this arrangement, the ejector includes a nozzle and a diffuser whichare formed as separate members respectively and which are coaxiallyassembled into a hole of a body respectively.

An explanation will be made schematically about an operation of such aconventional vacuum supply apparatus.

Compressed air is supplied to the ejector via the valve mechanismsection to generate a negative pressure. The negative pressure generatedin the ejector is applied to the suction pad via the tube connected tothe vacuum port. The suction pad attracts and holds a workpiece inaccordance with the action of the negative pressure generated in thesuction pad. While the suction pad is attracting and holding theworkpiece, a robot arm displaces the workpiece to transport theworkpiece to a predetermined position.

Subsequently, in order to release the workpiece, compressed air(positive pressure) is supplied to the suction pad from the valvemechanism section via a passage communicated with the vacuum port, andthus an effect of the negative pressure of the suction pad is decreasedand eliminated. As a result, the suction pad releases the workpiece tolocate the workpiece to a desired position.

There has been hitherto a need to achieve a small size and a lightweight as far as possible by reducing the outer diameter dimension, andto decrease the production cost by reducing the number of assemblingsteps. It is because, for example, when a plurality of vacuum supplyapparatuses are provided in a row to construct a manifold, it ispossible to obtain a solenoid valve manifold having an extremely smallsize and a light weight, and to effectively utilize the installationspace by reducing the outer diameter dimension of the entire apparatus.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide avacuum-generating unit capable of achieving a small size and a lightweight by reducing the outer diameter dimension of the entire apparatusand capable of reducing the production cost.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view illustrating a vacuum-generating unitaccording to an embodiment of the present invention;

FIG. 2 shows a side elevational view, partly cut away, taken in theaxial direction of the vacuum-generating unit shown in FIG. 1;

FIG. 3 shows a fragmental longitudinal sectional view illustrating anejector shown in FIG. 2;

FIG. 4 shows a fragmental side view, partly cut away, illustrating astate in which a pressure sensor is detachably installed to a tubejoint;

FIG. 5 shows a fragmental longitudinal sectional view illustrating anejector according to a modified embodiment of the present invention; and

FIG. 6 shows a fragmental longitudinal sectional view illustrating anejector according to a comparative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2, reference numeral 10 indicates a vacuum-generatingunit according to an embodiment of the present invention.

The vacuum-generating unit 10 comprises: a main body 20 including afirst block member 12, a second block member 14, and a third blockmember 16 formed of resin materials and connected to each other in thelongitudinal direction; a solenoid valve assembly 26 including apressure fluid-supplying solenoid valve 22 and a vacuum-breakingsolenoid valve 24 arranged on the upper portion of the main body 20; anejector 32 including a nozzle hole 28 and a diffuser hole 30 (see FIG.2) integrally formed (i.e., formed in a single component) in the thirdblock member 16; and a detector 34 for detecting a negative pressurederived from a vacuum port as described later on.

The pressure fluid-supplying solenoid valve 22 and the vacuum-breakingsolenoid valve 24 have the same components respectively, and they areclosed in a normal state. The solenoid valves 22, 24 are not limited tothe above normally closed type. The solenoid valves 22, 24 may be openin a normal state, self-retained, or timer-equipped, for example.

The first to third block members 12, 14, 16 have substantially the samewidth respectively, and they are formed to be thin-walled (see FIG. 1).The first block member 12 includes a compressed air supply port(pressure fluid supply port) 36 for supplying compressed air (positivepressure) to the ejector 32.

The second block member 14 includes a first ON/OFF valve 42 in a chamber40 therein, and the first ON/OFF valve 42 is switched from an OFF stateto an ON state by applying a pilot pressure thereto. The third blockmember 16 includes an unillustrated second ON/OFF valve in a chamberthereof, and the second ON/OFF valve is switched from an OFF state to anON state by applying a pilot pressure thereto.

The compressed air supply port 36 communicates with the inside of thechamber 40 of the second block member 14 arranged with the first ON/OFFvalve 42, via a first passage 48 having a substantially L-shaped bentform. An unillustrated second passage, which is branched from the firstpassage 48, is formed to communicate with the pressure fluid-supplyingsolenoid valve 22. An unillustrated third passage, which is branchedfrom the first passage 48, is formed to communicate with thevacuum-breaking solenoid valve 24. An unillustrated fourth passage,which is branched from the first passage 48, is formed to communicatewith the second ON/OFF valve (not shown).

As shown in FIG. 2, a first pilot passage 58 is formed between thepressure fluid-supplying solenoid valve 22 and the first ON/OFF valve42. The solenoid valve 22 applies a pilot pressure to the first ON/OFFvalve 42 through the first pilot passage 58 when energized to be in theON state. A second pilot passage 60 is formed between thevacuum-breaking solenoid valve 24 and the unillustrated second ON/OFFvalve. The solenoid valve 24 applies a pilot pressure to the secondON/OFF valve (not shown) through the second pilot passage 60 whenenergized to be in the ON state.

The ejector 32 is provided in the third block member 16 which isintegrally formed, for example, by means of resin molding. As shown inFIG. 3, the ejector 32 includes the nozzle hole 28 and the diffuser hole30, both of which are formed in an integrated manner in the third blockmember 16. The nozzle hole 28 and the diffuser hole 30 are arrangedcoaxially respectively. The nozzle hole 28 includes an orifice having asmall diameter. On the other hand, the diffuser hole 30 includes a holehaving a diameter larger than that of the nozzle hole 28 and apredetermined length in the axial direction.

A suction passage 64 is formed between the nozzle hole 28 and thediffuser hole 30 which constitute the ejector 32. The suction passage 64is communicated with a vacuum port 62 and is bent in a substantiallyL-shaped form. A negative pressure generated in the ejector 32 isapplied to a suction mechanism such as an unillustrated suction padconnected to a tube joint 65 via a tube, for example.

An exit end of the diffuser hole 30 is communicated with an exhaust port(discharge port) 66 formed in the third block member 16. The compressedair supplied to the ejector 32 is exhausted outside via a silencer 68communicated with the exhaust port 66.

When the vacuum-breaking solenoid valve 24 is in the ON state, a pilotpressure is applied to the unillustrated second ON/OFF valve. When thepilot pressure is applied, the unillustrated second ON/OFF valve becomesthe ON state, and a compressed air (positive pressure) is supplied tothe suction passage 64 communicated with the vacuum port 62.Accordingly, an effect of the negative pressure is decreased andeliminated.

The first ON/OFF valve 42 and the unillustrated second ON/OFF valve havethe same components respectively. Each of the valves includes: a valveplug 72 displaceable by a predetermined distance in a substantiallyhorizontal direction; and a retainer 74 fixed in the chamber 40 andformed to be cylindrical so that the valve plug 72 is surrounded thereby(see FIG. 2).

A first ring member 78 is installed to the outer circumferential surfaceof the valve plug 72 on one end side. The first ring member 78 is seatedon a seat section 76 of the retainer 74 to close the chamber 40. Asecond ring member 80 is installed to the outer circumferential surfaceof the valve plug 74 on the other end side. The second ring member 80 isslidable along the inner wall surface of the retainer 74. Each of thefirst and second ring members 78, 80 is made of an elastic material suchas natural rubber and synthetic rubber.

When the first ON/OFF valve 42 is in the OFF state, the supply of thecompressed air to the ejector 32 is stopped. When the first ON/OFF valve42 is in the ON state, the compressed air is supplied to the ejector 32.

The detector 34 includes a pressure sensor 82 for detecting the negativepressure to be applied to the suction pad via an unillustratedcommunication passage communicated with the suction passage 64. As shownin FIG. 4, the pressure sensor 82 is detachably installed to a tubejoint 84 connected to the third block member 16 by the aid of a screwportion. A detection signal outputted from the pressure sensor 82 istransmitted, for example, to an unillustrated external controller via alead wire 86.

In this arrangement, since the pressure sensor 82 is detachablyinstalled by the aid of the tube joint 84, it is possible to achieve asmall size and a light weight of the entire apparatus as compared withan arrangement in which an unillustrated vacuum switch is installed. Anoperator can arbitrarily select a pressure sensor 82 corresponding to anegative pressure range of the negative pressure derived from the vacuumport 62. Further, it is possible to conveniently replace with anotherpressure sensor 82.

As shown in FIG. 2, a flow rate-adjusting screw 88 for adjusting a flowrate of a pressure fluid (i.e., pilot pressure) for breaking the vacuumis provided between the pressure fluid-supplying solenoid valve 22 andthe vacuum-breaking solenoid valve 24. When a knob 88 a of the flowrate-adjusting screw 88 is gripped and rotated in a predetermineddirection, a tapered portion 88 b, which faces the passage 60, can bedisplaced in the vertical direction by screwing the screw 88 withrespect to a cylinder 90 to adjust the flow rate of the pressure fluidflowing through the passage 60.

The vacuum-generating unit 10 according to the embodiment of the presentinvention is basically constructed as described above. Next, itsoperations, functions, and effects will be explained. It is assumed thateach of the pressure fluid-supplying solenoid valve 22 and thevacuum-breaking solenoid valve 24 is in the OFF state in the initialstate.

Compressed air supplied from an unillustrated compressed air supplysource is introduced into the first passage 48 via the compressed airsupply port 36. The compressed air introduced into the first passage 48is supplied into the chamber 40 of the first ON/OFF valve 42communicated with the first passage 48. The valve plug 72 is displacedin the leftward direction in FIG. 2 under the action of the compressedair, but the first ON/OFF valve 42 is still in the OFF state.

In the above state, the unillustrated controller outputs an ON signal tothe pressure fluid-supplying solenoid valve 22 to start a pressurefluid-supplying operation. In this situation, the vacuum-breakingsolenoid valve 24 is still in the OFF state.

When the pressure fluid-supplying solenoid valve 22 becomes the ONstate, a pilot pressure is applied to the first ON/OFF valve 42 via thefirst pilot passage 58. The valve plug 72 is displaced in the rightwarddirection in FIG. 2 under the pilot pressure, so that the first ON/OFFvalve 42 becomes the ON state. When the first ON/OFF valve 42 is in theON state, then the compressed air introduced into the first passage 48passes through the first ON/OFF valve 42, and the compressed air issupplied to the ejector 32.

In the ejector 32, the compressed air is jetted from the nozzle hole 28toward the diffuser hole 30 to generate a negative pressure. Thenegative pressure is applied to the unillustrated suction pad via thesuction passage 64 and the tube connected to the vacuum port 62.

Therefore, the suction pad makes contact with the workpiece inaccordance with the operation of the unillustrated robot arm. When thesuction pad attracts and contacts the workpiece under the negativepressure, the negative pressure is further raised. The negative pressureis detected by the pressure sensor 82 of the detector 34. A detectionsignal is transmitted from the pressure sensor 82 to the unillustratedcontroller. When the controller receives the detection signal from thepressure sensor 82, it is confirmed that the suction pad reliablyattracts and holds the workpiece.

Next, an explanation will be made about a situation in which thenegative pressure of the suction pad is shut off to separate theworkpiece therefrom at a predetermined position after moving theworkpiece by a predetermined distance.

The unillustrated controller transmits an OFF signal to the pressurefluid-supplying solenoid valve 22. As a result, the solenoid valve 22becomes the OFF state, and thus the first ON/OFF valve 42 becomes theOFF state. Accordingly, the supply of the compressed air to the ejector32 is stopped, and thus the application of the negative pressure fromthe vacuum port 62 to the suction pad is stopped.

On the other hand, the unillustrated controller transmits an ON signalto the vacuum-breaking solenoid valve 24 so that the solenoid valve 24is in the ON state. When the solenoid valve 24 is in the ON state, apilot pressure is applied to the unillustrated second ON/OFF valve viathe second pilot passage 60. The valve plug 72 of the second ON/OFFvalve is displaced under the pilot pressure, and the second ON/OFF valvebecomes the ON state. When the second ON/OFF valve is in the ON state,the compressed air introduced into the first passage 48 is supplied tothe vacuum port 62 through the second ON/OFF valve. As a result, thecompressed air supplied from the compressed air supply port 36 passesthrough the vacuum port 62, and the compressed air is supplied to thesuction pad. The suction pad stops attracting the workpiece andseparates the workpiece therefrom.

When the suction pad separates the workpiece therefrom, the pressure ofthe suction pad changes the negative pressure to an atmosphericpressure. The pressure sensor 82 detects the atmospheric pressure andtransmits a detection signal to the unillustrated controller to indicatethe fact that the workpiece is separated. When the controller receivesthe detection signal, it is confirmed that the suction pad separates theworkpiece therefrom. Thus, it is possible to reliably separate theworkpiece from the suction pad.

In the embodiment of the present invention, the nozzle hole 28 and thediffuser hole 30 are integrally formed or formed in a single component,for example, by using a mold for molding resin, in the third blockmember 16 of the main body 20. Accordingly, it is possible to realize asmall size and a light weight of the entire apparatus. Therefore, it ispossible to effectively utilize the space in which the vacuum-generatingunit 10 is installed.

It is a matter of course that a plurality of the vacuum-generating units10 according to the embodiment of the present invention are connected ina row to construct a manifold.

Next, an explanation will be made while making comparison between anejector 100 according to a modified embodiment of the present inventionshown in FIG. 5 and an ejector 200 concerning a comparative embodimentshown in FIG. 6.

In the ejector 100 according to the modified embodiment, a nozzle hole104 and a diffuser hole 106 are formed coaxially in an integrated mannerin a single block member 102 composed of a resin material. A suctionport 108 is formed between the nozzle hole 104 and the diffuser hole106. A supply port 110 for supplying a pressure fluid to the nozzle hole104 is formed on one side of the block member 102. A discharge port 112for discharging the pressure fluid derived from the diffuser hole 106 isformed on the opposite side of the block member 102.

The ejector 200 concerning the comparative embodiment comprises twomembers of a block member 203 having a diffuser hole 202 formed therein,and a nozzle 210 formed with a nozzle hole 208 and connected to theblock member 203 in an air-tight manner by the aid of an O-ring 206 inan opening 204 of the block member 203. A supply port 212 and the nozzlehole 208 are formed integrally in the nozzle 210. The nozzle 210 isinserted into the opening 204 of the block member 203 by the aid of ascrew portion 214.

The block member 203 is formed with a suction port 216 which iscommunicated with the opening 204, and a discharge port 218 which iscommunicated with the diffuser hole 202 respectively.

Therefore, in the ejector 100 according to the modified embodiment, thenozzle 210 and the O-ring 206 are unnecessary as compared with theejector 200 concerning the comparative embodiment. The ejector 100according to the modified embodiment can be constructed by only thesingle block member 102. Therefore, the number of parts is reduced, andit is unnecessary to perform the operation for assembling the nozzle 210to the block member 203. As a result, the ejector 100 according to themodified embodiment makes it possible to reduce the production cost byreducing the number of parts and reducing the number of assemblingsteps.

While the invention has been particularly shown and described withreference to preferred embodiments, it will be understood thatvariations and modifications can be effected thereto by those skilled inthe art without departing from the spirit and scope of the invention asdefined by the appended claims.

1. A vacuum-generating unit comprising: a main body provided with apressure fluid supply port connected to a pressure fluid supply source,a vacuum port connected to a suction mechanism, and a discharge port fordischarging a pressure fluid supplied from said pressure fluid supplyport to the outside; and an ejector for generating a negative pressurebased on said pressure fluid supplied from said pressure fluid supplyport, said ejector including a nozzle hole and a diffuser hole which areformed integrally in said main body.
 2. The vacuum-generating unitaccording to claim 1, wherein said main body includes a plurality ofblock members composed of resin materials, and said nozzle hole and saiddiffuser hole are integrally formed in one of said block members.
 3. Thevacuum-generating unit according to claim 1, further comprising apressure sensor for detecting said negative pressure derived from saidvacuum port, wherein said pressure sensor is detachably and exchangeablyconnected to said main body by the aid of a tube joint.
 4. Thevacuum-generating unit according to claim 1, wherein said nozzle holeand said diffuser hole are arranged coaxially respectively, said nozzlehole including an orifice, and said diffuser hole having a diameterlarger than that of said nozzle hole and a predetermined length in anaxial direction.
 5. The vacuum-generating unit according to claim 4,wherein said discharge port is formed at an exit end of said diffuserhole, and a silencer is provided to discharge said pressure fluidsupplied from said discharge port to the outside.
 6. Thevacuum-generating unit according to claim 1, wherein a suction passageis formed between said nozzle hole and said diffuser hole.
 7. Thevacuum-generating unit according to claim 1, wherein saidvacuum-generating unit is connected in a row to anothervacuum-generating unit to construct a manifold.